Apparatus and methods for sweeping mines



NOV. 2, 1965 K, JR 3,215,112

APPARATUS AND METHODS FOR SWEEPING MINES Filed Jan. 30, 1962 2 Sheets-Sheet 1 116:1.

Elmemifieck, J7.

ATTORNEY Nov. 2, 1965 E. A. BECK, JR 3,215,112

APPARATUS AND METHODS FOR SWEEPING MINES Filed Jan. 30, 1962 2 SheetsSheet 2 ATTORNEY United States Patent 3,215,112 APPARATUS AND METHODS FOR SWEEPING MINES Elmer A. Beck, Jr., Park Ridge, 11]., assign'or, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed Jan. 30, 1962, Ser. No. 169,983 2 Claims. (Cl. 114-240) This invention relates to mine sweeping, and is concerned more particularly with the sweeping of pressureactuated mines.

Such a mine is planted on the ocean bottom and is designed to be triggered in response to a reduction in ambient pressure resulting when a cargo ship or other vessel of substantial tonnage passes near the mine.

It is an object of the invention to provide inexpensive apparatus and methods for sweeping pressure-actuated mines.

An additional object is to provide for sweeping of a pressure-actuated mine with little or no danger to the sweeping instrumentality.

Further objects and advantages of the invention will appear as the description proceeds.

- The invention will be better understood on reference to the following description and the accompanying drawing, wherein:

FIG. 1 is a diagrammatic view of a pressure-activated mine capable of being swept in accordance with the invention.

FIGS. 2 and 3 are respectively top plan and side elevational somewhat schematic views, partly broken, of one form of the invention.

FIGS. 4 and 5 are respectively similar to FIGS. 2 and 3 but show another form of the invention.

Referring now more particularly to the drawing, there is shown a pressure influence mine (FIG. 1) of the type' capable of being swept in accordance with the invention and comprising a main section 12, including among other things explosive and detonating means, and a hollow hermetically closed tail 16 including among other things a constant-viscosity electrically insulating liquid.

The tail 16 comprises a rigid sleeve 18 closed at its free end 20 by a very flexible corrugated rubber diaphragm 22 exposed at its outer face 24 to the sea 26, the sleeve being closed at its other end 28 by an air bellows 30 backed by a spring 32, the end 28 having a hole 34 establishing communication between the interior of the bellows and the interior of the main section 12. A partition 36 secured to the sleeve 18 divides the tail 16 int-o two compartments 38 and 40. The compartment 38 has end bells 42 and 44 connected by a tube 46, and the compartment 40 has end bells 48 and 50 connected by a tube 52.

A very flexible bellows 56 in the bell 44 is mounted on the partition 36, and the partition has a hole 58 therethrough communicating with the interior of the bellows. A plunger or piston 60 is neutrally buoyantly supported axially in the hole 58 by an assembly of springs 62 located in the bell 48 and anchored to the piston and to the partition 36, the annular clearance passage 64 between the piston and the wall of the hole being of relatively small radial extent but shown exaggerated.

A metal lever or beam 68 in the bell 48 is intermediately fulcrumed at 70 relative to the partition 36 and pivoted at one end 72 to a stiff gas-filled bellows 74 closed by and secured to the partition, and has at its free .end a contact 76 which, with a contact 78 borne by the piston 60, forms a switch 80 normally held closed by pressure exerted by the springs 62.

The annular passage 64 and a shunt bleeder hole 84 3,215,112 Patented Nov. 2, 1965 in the partition 36 afford the only means of communication between the compartment or liquid pressure region 38, which includes the interior of the bellows 56, and the liquid pressure region 86, which is that portion of the compartment 40 which is outside the bellows 30 and 74.

The mine section 12 houses electrically detonated explosive and circuitry therefor controlled by the switch as will appear. The switch beam 68 and one of the springs 62 are connected to a battery and a relay solenoid 92. The switch 80 being normally closed, the solenoid 92 is normally energized and holds open a relay switch 94 in series with a timer 96 and a battery 98. In parallel with this series circuit is a series circuit comprising a normally open timer-controlled switch 100 and a relay solenoid 102. The switch 100 consists of a contact 104, rotating with the timer 96, and a stationary contact 106 connected to the solenoid 102, which controls a normally open relay switch 108 in series with a detonator 110 and a battery 112.

While the tail switch 80 is closed, the detonator control switch 108 is open. When the tail switch 80 opens, the timer control relay switch 94 closes. As long as the switch 80 remains open, the switch 94 remains closed; if the switch 80 remains open long enough, the switch 94 will remain closed long enough to enable the timer-controlled switch 100 to close, thereby closing the relay switch 108 and firing the detonator 110. The period during which the switch 80 is kept open (by reason of the movement of a ship of suflicient length and tonnage, such as a cargo or troop ship, near the planted mine 10, as will appear) to assure explosion of the mine is such that the mine will explode substantially before the ship has traveled its own length, so that the mine will seriously damage or destroy the ship. If the switch 80 recloses before detonation, the timer-controlled switch 100 will return to its fully open condition.

As the mine 10 sinks in the sea, the increasing sea pressure is immediately communicated by the very flexible diaphragm 22 to the liquid in the region 38, and bleeding through the passage 84 ensues. With the increase in sea pressure as the mine sinks, the bellows 56 contracts, causing bleeding through the piston clearance passage 64 and exerting a force on the piston 60 in the direction to augment the pressure between the switch contacts 76 and 78. Due to the bleeding, the pressure in the region 86 is slowly increasing and causing contraction of the spring-backed bellows 30 and relatively slight contraction of the stiff bellows 74, tending somewhat to attenuate the pressure augmentation between the contacts 76 and 78. Within a few hours after the mine 10 is planted on the sea bottom 114, the bleeding will have brought the pressure in the region 86 to the ambient sea pressure, so that the hydraulic pressures on the piston ends will have equalized, and thus the position of the piston 60 will be influenced solely by the spring constant and the compression of the stiff bellows 74. The switch 80 will still be closed, but the pressure between the contacts 76 and 78 will be somewhat less than was the case before the mine 10 was submerged. It is thus apparent that the deeper the mine 10 is planted, the more will the stiff bellows 74 be compressed and hence the less will be the pressure between the contacts 76 and 78 when pressure equilibrium in the regions 38 and 86 is established. The significance of this fact will appear.

The surface water displaced by the plowing bow of a vessel undergoes a slight rise and then moves downward and comes up again to its normal level at the stern of the vessel. Due to friction with the vessel, this water at the same time undergoes a forward movement, and its flow may be considered as taking place between streamlines. The water below likewise moves between streamlines so that there is a field of streamlines due to the disturbance caused by the vessel. Accordingly, every point within the field in influenced by a velocity pressure due to such flow.

The pressure P on a submerged point is obtained by the equation P P iP where P is the hydrostatic pressure and P is the pressure due to the velocity of flow at the point, the sign being negative when the flow is past the point and positive when the fiow impinges on the point.

The switch 80 will open only pursuant to a reduction of pressure in the region 38 relative to that in the region 86 under certain conditions, as will appear.

Assume a planted mine whose regions 38 and 86 are in pressure equilibrium. When a marine vessel passing in the vicinity of the mine 10 causes flow of water at the mine past the diaphragm 22, the region 38 of course undergoes a pressure decrease without immediate appreciable effect on the pressure in the region 86. This decrease is referred to on occasion as a negative pressure. The negative pressure causes bleeding through the passage 84, and expansion of the bellows 56 and hence bleeding though the passage 64, from the region 86 into the region 38-, to slowly dissipate the pressure imbalance between the regions. The negative pressure is also responsible for movement of the piston 60 toward the region 38, reducing the force between the contacts 76 and 78 and thus tending to open the switch 80. The extent of such piston movement will depend on the magnitude of the negative pressure and the rate of its growth. A relatively slow drop in ambient sea pressure, as in the case of an ebbing tide, will have no appreciable effect on the position of the piston 60. A relatively rapid drop in ambient sea pressure, such as would be occasioned by a vessel moving in the vicinity of the mine 10, will cause movement of the piston 60 in the switch-opening direction; if the magnitude of the negative pressure is at least a predetermined minimum, the piston will move sufficiently to open the switch 80. Of course the aforementioned bleeding of liquid from the region 86 to the region 38 will continue, but at so low a rate that about half an hour, more or less, depending on the pressure differential in the regions, would transpire before the regions could achieve pressure equilibrium (if, of course, in the meanwhile the mine 10 had not exploded).

The displacement of the piston 60 is a function of the pressure differential in the regions 38 and 86, the pressure in the region 86, and the restoring force of the springs 62. When there is no pressure differential in the regions 38 and 86, the springs 62 hold the switch contacts 76 and 78 together with a force which depends on the spring constant and the compression of the stiff bellows 74. When there is a slight negative pressure, such, for example, as would be occasioned by an ebbing tide or a moving vessel of low tonnage, this force may relax somewhat but the switch 80 will remain closed. On the other hand, a negative pressure such as that resulting from passage of a cargo ship near the mine 10 will overcome the resistance offered by the springs 62 and thus open the switch 80.

It is apparent that, in order to achieve explosion of the mine 10, the negative pressure must grow at a sufliciently rapid rate and to such a magnitude as to open the switch 80 and be sustained long enough to hold the switch open for the period necessary to insure detonation of the mine. An explosion outside of the mine 10 might produce an adequate magnitude and rate of growth of negative pressure, but, the duration of the explosion being short, a negative pressure sufiicient to keep the switch 80 open will not be sustained for a suflicient length of time to enable the timer-controlled switch 100 to close; that is, the switch 80 will reclose and stop the timer 96 before the timer-controlled switch can close. A long barge or other relatively light weight long vessel will produce a negative pressure which may grow at the desired rate and be sustained, but its magnitude will be insufficient to effect opening of the switch 80. A moving vessel such as a cargo ship, however, having sufiicient tonnage and length, will fulfill all of the conditions needed to open the switch and keep it open long enough to insure detonation of the mine 10. Such a ship will cause a negative pressure in the region 38 of about 2 inches of water in about five seconds. Inasmuch as such mines will be planted in a harbor, the ship will be moving in the harbor at substantially below its cruising speed, and, if of a length of say 600 and moving at say 30 fps. (about '18 knots), will cause such negative pressure in the region 38 to be sustained for about twenty seconds The timer .96 is set to actuate the relay switch 108 in about ten seconds from inception of the negative pressure pulse, so that the mine 10 will fire while the ship is in position to receive substantially the full brunt of the mine explosion.

It is apparent from the foregoing that the magnitude of the negative pressure pulse necessary to open the switch 80 varies in an inverse manner with the depth of the planted mine 10. The deeper the mine 10, the less will be the negative pressure at the mine produced by the ship. Hence a mine 10 designed to be detonated by a moving ship having at least a predetermined tonnage will be detonated by such a ship irrespective of the planting depth, provided of course that the depth is such that hydrostatic pressure alone is insufficient to compress the stiff bellows 74 enough to open the switch 80. The planting depth will not exceed about 200'.

Prior to this invention, there was no generally satisfactory mechanism or technique for sweeping pressure influence mines. In accordance with the invention this is accomplished by means of a pressure signature generated by artificially created submerged fiow at the planted mine. The artificially generated pressure signature may simulate a ships pressure signature resulting from a negative pressure pulse on the outer face 24 of the diaphragm 22, or the artificially produced signature may take an equivalent form resulting from a positive pressure pulse on the outer face of the diaphragm, as will appear.

Means in accordance with one form of the invention for artificially creating submerged flow for activating the planted mine 10 is shown in FIGS. 2 and 3, and cornprises a small barge towed slowly (up to a few knots), preferably in the direction 122, as by a helicopter (not shown), and equipped with fuel-powered pumps 124 (shown diagramamtically). An intake pipe 126 immersed in the sea near the surface 128 at each side of the barge 120 is connected to a pair of the pumps 124. Extending from the several pumps 124 are discharge pipes 130 leading to a system or bank 134 of nozzles 136 whose discharge ends are lowermost and immersed in the sea, but near the water surface 128, and whose axes lie in one or more vertical planes normal to the direction of tow. The nozzles 136 are shown in a single row, but additional rows could be provided if desired.

The water jets discharging from the nozzles 136 expand and slow down with depth, and mushroom at the sea bottom 114. During the passage of the nozzle system 134 over the mine 10, the moving water impinging on the sea bottom 114 will cause the pressure ambient to the mine 10, and hence the pressure in the region 38 (FIG. 1), to undergo a sharp increase. The pumping pressure is such that this positive pressure pulse will approximate 10 inches of water, causing bleeding to the region 86 at a rapid rate, the rate of tow being small enough to sustain the pulse for about five seconds, long enough for sufficient bleeding to enable the pressure in the region 86 to increase by at least about 2 inches of water. On the passing of the nozzle system 134 and consequent prompt cessation of fiow at the mine 10, the region 38 will resume its normal static state pressure, which is at least about 2 inches of water below the new pressure in region 86. The region 38 thus being at a negative pressure of at least about 2 inches of water, the piston 60, as noted above in the discussion involving the ship-generated negative pressure pulse, is moved in the direction and to an extent to open the switch 80, which will remain open for the desired period before the relatively slow return bleeding from the region 86 to the region 38 will have reduced the pressure differential sutficiently (to about 0.7 inch of water) to enable the springs 62 to close the switch. If desired, the nozzles 136 could be inclined slightly to provide all or a substantial part of the barge-propelling force, without appreciably affecting the mine-sweeping eificacy of the nozzle system 134.

In accordance with another form of the invention (FIGS. 4 and 5), a small barge 140, towed slowly (up to a few knots) in the direction 142, as by a helicopter (not shown), is equipped with fuel-powered pumps 144 (shown diagrammatically). An intake pipe 146 immersed in the sea near the surface 128 at each side of the barge 140 is connected to a pair of the pumps 144. Each pair of pumps 144 drives the intaken water to a single outlet 148, the two outlets leading to a single discharge pipe 150. The pipe 150 inclines from the stern of the barge 140 down into the water to a level near the sea bottom 114 and terminates in a horizontal manifold 152 carried by a skid or sled 154 drawn along the bottom by the barge 140 as by a tow cable 156 connected to the sled runners 158. The manifold 152 has, at its opposite sides, horizontal nozzles 160 arranged in pairs, the nozzles of each pair being axially aligned and oppositely directed, all of the nozzle axes being coplanar with the manifold axis. Thus coplanar horizontal jets of water are produced near the sea bottom 114. The resulting flow at the mine will produce in the region 38 (FIG. 1) a positive or a negative pressure pulse, depending on whether the flow does or does not impinge on the diaphragm 22. If a positive pressure pulse is experienced by the region 38, the operation will be as described above with the nozzle system 134.

If, as is of course more likely to be the case, the diaphragm 22 is not facing the horizontal nozzle-created flow at the sea bottom 114, this fiow will cause a sharp reduction in the static head at the diaphragm, creating in the region 38 a negative pressure signature such as would be produced by a ship for whose destruction the mine is designed.

In each form of the invention the barge and equipment carried thereby are relatively inexpensive, and their tonnage is insufiicient to provide, merely by virtue of movement of the barge, sufficient pressure change at the mine 10 to activate the mine.

The artificially created horizontal jets near the sea bottom 114, could operate to bring about detonation of a mine 10 which has lain in a depression in the sea bottom long enough for the pressure in the region 86 to reach ambient sea pressure, if the depth of the depression is at least equal to the number of inches of negative pressure necessary to effect detonation of the mine. When the jets, impinging on the mine 10 broadside, force the mine out of the depression and onto the adjacent relatively ele vated bed surface, the region 38, in the short time it takes the mine to roll out of the depression, is reduced in pres sure relative to the region 86 by an amount equal to the depth of the depression. This pressure reduction will, as explained above, bring about detonation of the mine 10. If the mine 10 had been covered with silt, the jet streams Will remove the silt and roll the mine to a higher elevation.

It is apparent from the foregoing that the mine-sweeping apparatus employed in accordance with the invention is relatively inexpensive. Moreover, danger of damage to the equipment by the exploding mine is minimized inasmuch as the equipment will be beyond the spehre of damage when the mine explodes.

Within the purview of the invention a mine is considered planted when it is on the sea bottom and its regions 38 and 86 are at ambient sea pressure.

While preferred embodiments have been described in some detail, they should be regarded as examples of the invention and not as restrictions or limitations thereof as changes may be made in the construction and arrangement of the parts and methods without departing from the spirit and scope of the invention.

I claim:

1. In an apparatus for sweeping a mine of the pressureinfluenced type planted on the sea bottom, a vessel on the sea and incapable of influencing such a mine, means for moving the vessel along the sea, a sled on the sea bottom and connected to the vessel, nozzle means near the sea bottom and supported by the sled, and means on the vessel and connected to the nozzle means for pumping sea water to the nozzle means, the nozzle means being arranged to discharge water into the ambient sea horizontally normal to the path of the vessel, the pumping means being capable of forcing discharge of water from the nozzle means at a rate to create at the mine a pressure signature capable of activating the mine.

2. The structure of claim 1, characterized in that the nozzle means comprises one or more pairs of nozzles, the nozzles of each pair being arranged to discharge water into the ambient sea at the same depth and in opposite directions away from each other.

References Cited by the Examiner UNITED STATES PATENTS 1,310,326 7/19 Dibble 114-240 2,331,735 10/43 Schwab 114-240 3,012,534 12/61 Thomas 114-235 3,108,246 10/63 Jones 114-235 3,112,669 12/63 Damblanc 89-1 FOREIGN PATENTS 493,301 4/19 France.

FERGUS S. MIDDLETON, Primary Examiner.

BENJAMIN A. BORCHELT, SAMUEL FEINBERG,

Examiners. 

1. IN AN APPARATUS FOR SWEEPING A MINE OF THE PRESSUREINFLUENCED TYPE PLANTED ON THE SEA BOTTOM, A VESSEL ON THE SEA AND INCAPABLE OF INFLUENCING SUCH A MINE, MEANS FOR MOVING THE VESSEL ALONG THE SEA, A SLED ON THE SEA BOTTOM AND CONNECTED TO THE VESSEL, NOZZLE MEANS NEAR THE SEA BOTTROM AND SUPPORTED BY THE SLED, AND MEANS ON THE VESSEL AND CONNETED TO THE NOZZLE MEANS FOR PUMPING SEA WATER TO THE NOZZLE MEANS, THE NOZZLE MEANS BEING ARRANGED TO DISCHARGE WATER INTO THE AMBIENT SEA HORIZONTALLY NORMAL TO THE PATH OF THE VESSEL, THE PUMPING MEANS BEING CAPABLE OF FORCING DISCHARGE OF WATER FROM THE NOZZLE MEANS AT A RATE TO CREATE AT THE MINE A PRESSURE SIGNATURE CAPABLE OF ACTIVATING THE MINE. 